jQuery UI accordion - Not quite working as expected

jQuery UI accordion - Not quite working as expected

Hi guys, 

Just wondering if you would help me out here. 

I'm not bad with jQuery, and I've used the jQuery UI before, but this is my first time using an accordion. 

Basically what I'm trying to achieve is this:

The black header is essentially the active link, and the box beneath it is the div containing links that correspond to that header action. So under 'Manage News' there might be 'Add News' etc. 

The other silver links would be other sections, such as 'Manage Blog' or something like that.

Now, at the minute I have the accordion working insofar as that it is running, but it's not quite doing what I expect. It seems to be collapsing two things at a time and then breaking on others.

The working example is here:

In case you were wondering, yes, I'm trying to build a basic CMS for my final year project at Uni =]

Thanks for your help in advance!